The invention relates to check valves and more particularly to check valves designed to function as a heart valve prosthesis.
A wide variety of heart valves have been developed that operate hemodynamically as a result of the pumping action of the heart. Some of the earliest valves were of the ball and cage design, as exemplified by U.S. Pat. No. 3,416,159, issued Dec. 17, 1968. Thereafter, a wide variety of valves which utilized one or more disc-shaped occluders were developed, as exemplified by U.S. Pat. No. 3,367,364, issued Feb. 6, 1968. Somewhat more recently, valves utilizing a pair of pivoting leaflets were developed--such as those shown in U.S. Pat. No. 4,159,543, issued July 3, 1979, and in U.S. Pat. No. 4,178,639, issued Dec. 18, 1979. U.S. Pat. No. 4,178,638, issued Dec. 18, 1979, is exemplary of a heart valve using a pair of curved leaflets which pivot about central hinge points.
The fairly large number of patents in this area is evidence of the fact that the search goes on for improved heart valves which have prompt response, exhibit low pressure drop in the open position and do not develop localized wear.